As is well known in medical circles, one of the more important blood components to measure for diagnostic purposes is glucose, especially for diabetic patients. The well-known and typical technique for determining blood glucose concentration is to secure a blood sample and apply that blood to an enzymatically medicated colorimetric strip or an electrochemical probe. Generally, this is accomplished from a finger prick. For diabetic patients who may need to measure blood glucose a few times a day, it can immediately be appreciated that this procedure causes a great deal of discomfit, considerable irritation to the skin and, particularly, the finger being pricked, and, of course, infection.
For many years, there have been any number of procedures for monitoring and measuring the glucose level in humans and animals. These methods, however, generally involve invasive techniques and, thus, have some degree of risk, or at least some discomfit, to the patient. Recently, some non-invasive procedures have been developed, but still they do not always provide optimum measurements of the blood glucose. At present there is no practical, confirmed solution.
Thomas (U.S. Pat. No. 5,119,819) teaches a non-invasive method of monitoring blood glucose, but it is based on only an acoustic velocity measurement based on the two-way travel time of an ultrasound pulse.
Gozani (U.S. Pat. No. 5,771,891) discloses a non-invasive method for blood analyte measurement. First, there is electrical stimulation of an endogenous tissue and then the detection of the resulting electrical response to the stimulus. One embodiment shows electrical stimulation of a hypoxic peripheral nerve, and then the detection of the resulting Compound Action Potential elsewhere along the nerve.
Cho (U.S. Pat. Nos. 5,795,305 and 5,924,996) uses combined temperature and measurements of either infrared radiation or thermal conductivity to determine the glucose concentration.
Chou (U.S. Pat. Nos. 5,941,821 and 6,049,728) determines the blood glucose by a photoacoustic measurement in which the acoustic pulse is generated by heating the patient's skin with electromagnetic radiation.
In each of these prior art techniques, only one (or in one case two) parameters are measured. Thus, the possibility of an error is increased. The instant invention uses measurements of three distinct parameters to determine the blood glucose level, thereby substantially increasing the accuracy of the measurement. Moreover, none of the prior art techniques utilize any measurement of electrical conductivity and heat capacity, which are two of the parameters measured in the instant invention.
Therefore, there is a need for a more accurate non-invasive procedure for measuring glucose level, by means of monitoring multiple parameters.